Transient evolution of C-type shocks in dusty regions of varying density
Transient evolution of C-type shocks in dusty regions of varying density
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不同密度尘埃区C型激波的瞬态演化
DOI：
10.1051/0004-6361/200913277
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发表时间：
2010
影响因子：
6.5
通讯作者：
Ashmore I
中科院分区：
文献类型：
--
作者：
Ashmore I
年轻恒星的外流将冲击驱动到尘埃分子区域。这种冲击的大多数模型都受到这样的假设的限制，即它们是稳定的，并且在垂直于磁场的方向上传播。然而，激波传播的介质是不均匀的，激波是不稳定的。此外，只有一小部分的冲击是近vertical.AimsWe识别功能时，遇到的冲击密度不均匀性，并确定是否有任何部分的非稳态多流体冲击的前体区域以往任何时候都表现在一个准稳态的方式。如果它这样做，一些随时间变化的冲击可能是近似建模，而不解决随时间变化的hydromagnetic equations.MethodsWe使用的代码采用以前产生的第一个随时间变化的模拟快模式斜C型shocks包括一个自洽计算的热和电离平衡和流体处理grains.ResultsSimulations最初稳定斜C型shocks，其中每一个都遇到三种类型的密度不均匀性中的一种。对于密度大于周围介质密度的半有限不均匀体，透射激波在与离子流时间相当的时间尺度上从J型激波演化为稳定的C型激波，演化J型激波前体的足够上游部分是准稳定的。离子流的时间尺度也与冲击波向密度递减区域的演化有关。冲击传播到区域中的密度增加，然后减少到其初始值的模型不能完全描述的单调增加和减少density.ConclusionsWe的结果，我们提出的第一个依赖于时间的模拟尘埃C-型冲击与密度扰动相互作用。我们研究了激波结构的瞬态演化，发现初始相互作用总是产生向J型激波的转变。此外，回到C型激波的长期演化并不总是可用准定常模型来近似。
ContextOutflows of young stars drive shocks into dusty, molecular regions. Most models of such shocks are restricted by the assumptions that they are steady and propagating in directions perpendicular to the magnetic fields. However, the media through which shocks propagate are inhomogeneous and shocks are not steady. Furthermore, only a small fraction of shocks are nearly perpendicular.AimsWe identify features that develop when a shock encounters a density inhomogeneity and ascertain if any part of the precursor region of a non-steady multifluid shock ever behaves in a quasi-steady fashion. If it does, some time-dependent shocks may be modelled approximately without solving the time-dependent hydromagnetic equations.MethodsWe use the code employed previously to produce the first time-dependent simulations of fast-mode oblique C-type shocks including a self-consistent calculation of the thermal and ionisation balances and a fluid treatment of grains.ResultsSimulations were made for initially steady oblique C-type shocks, each of which encounters one of three types of density inhomogeneities. For a semi-finite inhomogeneity with a density larger than the surrounding medium's, a transmitted shock evolves from being of J-type to a steady C-type shock on a timescale comparable to the ion-flow time through it. A sufficiently upstream part of the precursor of an evolving J-type shock is quasi-steady. The ion-flow timescale is also relevant for the evolution of a shock moving into a region of decreasing density. The models for shocks propagating into regions in which the density increases and then decreases to its initial value cannot be entirely described in terms of the results obtained for monotonically increasing and decreasing densities.ConclusionsWe present the first time-dependent simulations of dusty C-type shocks interacting with density perturbations. We studied the transient evolution of the shock structure and find that the initial interaction always produces a transition to a J-type shock. Furthermore, the long-term evolution back to a C-type shock cannot always be approximated by quasi-steady models.
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DOI：
10.1086/382784
发表时间：
2004
期刊：
The Astrophysical Journal Letters
影响因子：
--
作者：
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通讯作者：
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DOI：
10.1086/304595
发表时间：
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影响因子：
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作者：
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DOI：
10.1046/j.1365-8711.1998.01391.x
发表时间：
1998
影响因子：
4.8
作者：
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影响因子：
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作者：
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DOI：
10.1046/j.1365-8711.1998.01641.x
发表时间：
1998
影响因子：
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作者：
M. Wardle
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